Today developer theheroGAC has released a new version of PRXshot v0.4.1 for the Playstation Vita. Check out the release notes, changelog and the download link provided below.

Release Notes
Download the plugin at the end of the article.
Insert the plugin into ux0:/pspemu/seplugins (if the seplugins folder does not exist you must create it)
Edit the GAME.TXT and vsh.txt files by adding the following string (if the two files do not exist you must create them)
ms0:/seplugins/prxshot.prx 1
Well you are done. Now you can make screenshots. Screenshots are stored in the path
ux0:/pspemu/PSP/SCREENSHOTS
Changelog
Added compatibility with Adrenaline 6
To make a screenshot, press L+R